To answer your second question first: yes you should partition. Oracle's query optimizer has a feature called partition elimination, which will check the predicate for the partition and only execute the SQL on the appropriate partitions.
Partitioning also leaves all the data in one space. Conceptually, think of it as many tables of identical structure, with an implicit UNION ALL between them if you were to do a SELECT from the entire table. Except "under the hood" Oracle sorts the actual rows into the right "table" based on the criteria you specify. Any rows that come in that don't match any of the criteria, go into what's known as the "default" partition.
For what you want to do, a "range partition" might be a good approach (so you can add more tenants later), e.g.:
create table transaction (id, tenant_id, a, b, c, d)
partition by range(tenant_id)
partition p_tenant1 values less than (2) tablespace ts_tenant1
partition p_tenant2 values less than (3) tablespace ts_tenant2
partition p_tenant3 values less than (4) tablespace ts_tenant3
partition p_tenantd values less than (MAXVALUE) tablespace ts_default;
Then later
alter table transaction
add partition p_tenant4 values less than (5) tablespace ts_tenant4;
This will create something that looks and behaves just like a normal table, but actually rows where tenant_id=1 will be in a partition in tablespace ts_tenant1, and queries will ignore all other partitions. Queries across the entire table can run in parallel on each partition. If tenant_id=4 in this scenario, the row will live in ts_default unless you add the new partition as shown, but the INSERT won't be rejected because there's no partition for it!
FWIW At my site we use partitioned tables in our 40Tb DW, you don't need to worry about this approach scaling or performing, if you choose your partitioning strategy well (e.g. you could partition on tenant_id then subpartition on month perhaps), create the right indexes, and so on.
You really don't need partitioning for this to work efficiently, which is what I told you on your last question as well...even if you have billions of rows.
If you cluster on the BarcodeID (which I am assuming is unique) and put a nonclustered index on LoyaltyCardID it should work just fine. These are NOT complicatd queries with a lot of additional logic from the sounds of things, and simple seek operations are extremely efficient on their own.
Are you getting pressure to partition or is it just something that you have decided to do?
Best Answer
jkavalik is right.
I'll say it more strongly:
PARTITION BY HASHis possibly useless in any situation for enhancing performance.Your table is referenced only by the
PRIMARY KEY(id), correct? And it is InnoDB, correct? If you have a million rows, the BTree that contains the PK and all the data is about 3 levels deep. For a _trillion_rows, it will be about 6 levels.The million-fold increase in data size (from 1M to 1T) might slow down a "point query" by a factor of 2. That's all.